Joshua trees are a central component of the Mojave ecosystem. The trees rely on one species of moth almost exclusively for pollination, and the moth relies completely on the Joshua tree flowers as a nursery to for its larvae. After big blooms like this, rodent populations boom on an abundance of seeds.

(Image: David Danelski/AP/PA)

Cameron Barrows, an ecologist at the University of California Riverside, Palm Springs, says that water is the limiting factor for Joshua trees, and given recent shortages, this may not be an ordinary event. "Blooms like this are filled with water," he says. "They are flush with nectar, with odours to attract insects. So if you are water stressed, it seems you'd want to conserve that - unless this is your last shot."

Further north in Nevada, Todd Esque of the United States Geological Survey says persistent drought is unlikely to be the only factor behind the bloom, but that it's hard to know, as there's no record of bloom magnitudes and timings to compare against. "This is a natural cycle in the desert," says Esque. "A great series of things have to coincide for the Joshua trees to survive."